OpenWrt – Rev 4
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From: Felix Fietkau <nbd@nbd.name>
Subject: netfilter: match bypass default table
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
net/ipv4/netfilter/ip_tables.c | 79 +++++++++++++++++++++++++++++++-----------
1 file changed, 58 insertions(+), 21 deletions(-)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -248,6 +248,33 @@ struct ipt_entry *ipt_next_entry(const s
return (void *)entry + entry->next_offset;
}
+static bool
+ipt_handle_default_rule(struct ipt_entry *e, unsigned int *verdict)
+{
+ struct xt_entry_target *t;
+ struct xt_standard_target *st;
+
+ if (e->target_offset != sizeof(struct ipt_entry))
+ return false;
+
+ if (!(e->ip.flags & IPT_F_NO_DEF_MATCH))
+ return false;
+
+ t = ipt_get_target(e);
+ if (t->u.kernel.target->target)
+ return false;
+
+ st = (struct xt_standard_target *) t;
+ if (st->verdict == XT_RETURN)
+ return false;
+
+ if (st->verdict >= 0)
+ return false;
+
+ *verdict = (unsigned)(-st->verdict) - 1;
+ return true;
+}
+
/* Returns one of the generic firewall policies, like NF_ACCEPT. */
unsigned int
ipt_do_table(struct sk_buff *skb,
@@ -268,24 +295,8 @@ ipt_do_table(struct sk_buff *skb,
unsigned int addend;
/* Initialization */
- stackidx = 0;
- ip = ip_hdr(skb);
- indev = state->in ? state->in->name : nulldevname;
- outdev = state->out ? state->out->name : nulldevname;
- /* We handle fragments by dealing with the first fragment as
- * if it was a normal packet. All other fragments are treated
- * normally, except that they will NEVER match rules that ask
- * things we don't know, ie. tcp syn flag or ports). If the
- * rule is also a fragment-specific rule, non-fragments won't
- * match it. */
- acpar.fragoff = ntohs(ip->frag_off) & IP_OFFSET;
- acpar.thoff = ip_hdrlen(skb);
- acpar.hotdrop = false;
- acpar.state = state;
-
WARN_ON(!(table->valid_hooks & (1 << hook)));
local_bh_disable();
- addend = xt_write_recseq_begin();
private = table->private;
cpu = smp_processor_id();
/*
@@ -294,6 +305,23 @@ ipt_do_table(struct sk_buff *skb,
*/
smp_read_barrier_depends();
table_base = private->entries;
+
+ e = get_entry(table_base, private->hook_entry[hook]);
+ if (ipt_handle_default_rule(e, &verdict)) {
+ struct xt_counters *counter;
+
+ counter = xt_get_this_cpu_counter(&e->counters);
+ ADD_COUNTER(*counter, skb->len, 1);
+ local_bh_enable();
+ return verdict;
+ }
+
+ stackidx = 0;
+ ip = ip_hdr(skb);
+ indev = state->in ? state->in->name : nulldevname;
+ outdev = state->out ? state->out->name : nulldevname;
+
+ addend = xt_write_recseq_begin();
jumpstack = (struct ipt_entry **)private->jumpstack[cpu];
/* Switch to alternate jumpstack if we're being invoked via TEE.
@@ -306,7 +334,16 @@ ipt_do_table(struct sk_buff *skb,
if (static_key_false(&xt_tee_enabled))
jumpstack += private->stacksize * __this_cpu_read(nf_skb_duplicated);
- e = get_entry(table_base, private->hook_entry[hook]);
+ /* We handle fragments by dealing with the first fragment as
+ * if it was a normal packet. All other fragments are treated
+ * normally, except that they will NEVER match rules that ask
+ * things we don't know, ie. tcp syn flag or ports). If the
+ * rule is also a fragment-specific rule, non-fragments won't
+ * match it. */
+ acpar.fragoff = ntohs(ip->frag_off) & IP_OFFSET;
+ acpar.thoff = ip_hdrlen(skb);
+ acpar.hotdrop = false;
+ acpar.state = state;
do {
const struct xt_entry_target *t;